Flexible Plate Making Process

Label printing covers several major printing methods at the plate making stage. According to the nature of different products, different printing methods are selected. For different printing methods, the plate making process is also different. This article gives a brief introduction to the flexography process.

The process flow of the flexographic plate making process is: manuscript → film (negative film) → exposure → rinsing → drying → post-processing.

1. Manuscript

The manuscript for flexible printing should have the following characteristics: more colors. However, there are few overprints; no special details are required to be reproduced; the cable is not too high, but color printing can be achieved; packaging can be done online.

2. Film (negative film)

In accordance with the needs of plate making, graphic and clear, accurate size and size specifications; with frosted film, film density requirements for the same film; the use of positive film; measured by transmission densitometer, the density of white bits below 0.06; black density of 3.5 or more.

3. Exposure includes back exposure and main exposure

1 back exposure

The support film of the photosensitive resin plate is up and the protective film is laid down in the exposure drawer to receive exposure. Ultraviolet light penetrates the support film to cure the photosensitive adhesive layer. In order to establish a stable base, the depth of platewashing can also be controlled, and the binding force between the support film and the photosensitive resin layer can be strengthened. The back exposure time is determined based on the required substrate thickness.

2 main exposure

Also known as front exposure, the photosensitive resin plate is supported with the film facing down and the protective film facing up. Tiled in the exposure drawer. The protective film is peeled off once and the film surface of the film is pasted on the photosensitive resin plate. The vacuum film inspection method is covered with a film (a non-membrane vacuum) so that the film is closely attached to the photosensitive resin layer. Ultraviolet rays pass through the vacuum film and the translucent part of the film, so that the photosensitive part of the plate is polymerized and cured. The length of the main exposure is determined by the plate type and the light source strength. If the exposure time is too short, the graphic gradient will be too straight, the lines will be curved, and the small prints and small dots will be washed away. On the other hand, if the exposure time is too long, the print will be distorted. If there are big and small, thick and thin lines on the same plate. Visible with black film cover the exposure. Small parts will not be lost due to flushing to ensure plate quality.

4. rinse

The unexposed part is washed and dissolved, leaving the photopolymerized relief. Washing time depends on the thickness of the printing plate and the depth of the impression. If the washing time is too short, the unsensitized resin will remain on the plate, which will affect the plate-making depth. If the plate-washing time is too long, the plate will swell, resulting in deformation of the fine part or Fall off.

5. drying

Remove the wash solvent and return the plate to its original size. The baking temperature is between 50-60°C. The baking time is determined by the thickness of the plate and the length of the plate-washing time, generally two hours thick and one hour thin. Too long baking time and too high baking temperature will make the printing plate brittle and affect the printing life. If the baking temperature is too low, the drying time will be prolonged, the baking time will be too short, and the printing will be rotted.

6. Post-processing

That is, in addition to sticking and post exposure. The photosensitive resin is completely hardened (polymerized) to achieve the required hardness index, and eliminate the tackiness of the printing plate to facilitate ink transfer. The post-processing time was obtained from the test with the aim of not cracking or sticking.